Effects of lactation stage and behavioral activity on enteric methane emissions in dairy cows.

This study investigated how the lactation stage and the main behavioral activities of dairy cows influence enteric methane emissions. The research trial was conducted on 39 Italian Simmental dairy cows reared in a commercial dairy farm. Each animal was monitored during early, mid, and late lactation. Methane emissions were measured using a Laser Methane SMART device (Tokyo Gas Engineering Solutions Ltd.). Simultaneously, eating, rumination, and resting times were continuously recorded using activity monitoring collars. Furthermore, milk yield and composition and feed samples were collected throughout the experiment. Methane emissions were significantly affected by both behavioral activity and its interaction with lactation stage. The highest methane intensity values were observed during rumination in late lactation, whereas resting consistently showed the lowest emissions. Emissions estimated by considering only eating activity tended to overestimate total daily methane output compared with estimates weighted across all behaviors. These findings underscore that behavioral patterns, particularly rumination and resting, contribute substantially to daily methane emissions and should be included in emissions models to improve the accuracy of environmental assessments and mitigation strategies in dairy production systems.